The present invention relates to heat exchangers and more particularly to heat exchangers used in the cooling circuits of thermal engines.
Heat exchangers or radiators having tubes placed horizontally and opening into tube plates covered by header tanks are used increasingly. It is frequent, taking in account the available space, particularly under the hood of a vehicle, that some of the horizontal tubes of the heat exchanger form the higher portion of the cooling circuit, and consequently, if the cooling circuit contains air, the air is found in the tubes of the upper rows.
In addition to the fact that this air reduces the thermal exchange capacity of the heat exchanger, it results in still more serious disadvantages. Actually, when hot liquid is conveyed to the heat exchanger, those of the tubes through which the liquid flows are abruptly expanded, in particular at their junction with the tube plates, whereas those containing air are not subjected at the same time to heat expansion, and the resulting differential heat expansion may frequently cause rupture of the connection between the tubes and the tube plates.